AMNA NAWAZ: Jury selection began today, as Democratic Senator Bob Menendez is set to become the first sitting senator ever tried for conspiracy to act as a foreign agent.

The case is expected to last several weeks.

Lisa Desjardins previews what's to come.

LISA DESJARDINS: In Manhattan today, a powerful New Jersey senator arrived to face everyday New Yorkers who will decide his fate.

The start of jury selection is the start of Democrat Bob Menendez's second bribery trial in seven years.

The senior senator was accustomed to calling the shots from his perch atop the Senate Foreign Relations Committee.

He stepped down as chair when charges came last fall.

But Menendez refuses to resign from office.

SEN. ROBERT MENENDEZ (D-NJ): I recognize this will be the biggest fight yet, but, as I have stated throughout this whole process, I firmly believe that, when all the facts are presented, not only will I be exonerated, but I still will be the New Jersey's senior senator.

LISA DESJARDINS: The lawmaker is charged with becoming a lawbreaker, accused of taking bribes to help individual businessmen, as well as Egypt and Qatar, and then greasing billions in weapons and other deals, passing along information and pressuring officials.

DAMIAN WILLIAMS, U.S. Attorney, Southern District of New York: My office remains firmly committed to rooting out public corruption without fear or favor and without any regard to partisan politics.

LISA DESJARDINS: Prosecutors say they found what Menendez and his wife got in exchange, a Mercedes convertible and, inside their house, gold bars worth 100 grand and wads totaling more than $480,000 in cash.

Menendez offered this explanation.

SEN. ROBERT MENENDEZ: For 30 years, I have withdrawn thousands of dollars in cash from my personal savings account, which I have kept for emergencies and because of the history of my family facing confiscation in Cuba.

LISA DESJARDINS: Prosecutors paint Menendez's wife, Nadine, as a critical go-between, but Menendez's court filings have hinted he may try to pin all the blame on her.

Her trial is set for July.

Two businessmen charged will be tried alongside the senator.

All four defendants have pleaded not guilty.

They may have been friends, but Menendez to stress they were also constituents.

JONATHAN SALANT, Former Washington Correspondent, NJ Advance Media: You cannot prosecute a lawmaker for talking on the floor and for acting as a lawmaker, including helping constituents.

LISA DESJARDINS: Jonathan Salant covered Menendez as the Washington correspondent for a group of New Jersey papers for nearly a decade, including the senator's last trial.

SEN. ROBERT MENENDEZ: To those who were digging my political grave so that they could jump into my seat, I know who you are and I won't forget you.

LISA DESJARDINS: Menendez survived that bribery case in 2017.

Prosecutors alleged that he took nearly a million dollars worth of gifts in exchange for helping a friend's business.

The DOJ did not retry the case after jurors deadlocked.

EDWARD NORRIS, Juror: It was a victimless crime, I think, and I just didn't see a smoking gun.

LISA DESJARDINS: Salant says, in this year's case, there is a change in Jersey political cycles.

JONATHAN SALANT: It was outrageous enough that the delegation called for his resignation, the governor called for his resignation.

So this goes -- in the opinion of those folks, goes beyond normal rough-and-tough New Jersey politics.

LISA DESJARDINS: Congressman Andy Kim is the prohibitive favorite to win New Jersey's Democratic primary this June.

Menendez is sitting out that race, but could run as an independent in November.

JONATHAN SALANT: If Menendez runs as an independent, that could scramble everything.

LISA DESJARDINS: Democrats face longer odds to keep the Senate if New Jersey becomes a battleground, but, for Menendez, much more than his political future is on the line.

If convicted on all charges, he could face a sentence of over 200 years.

For the "PBS NewsHour," I'm Lisa Desjardins.